Silica is a useful material for rice cultivation and the growth of some agricultural crops and has been used as silica fertilizer. In recent years, it has been pointed out that silica is an essential trace mineral not only for agricultural crops but also for the human body, and it has been pointed out that the value as food, medicine and cosmetics is increasing.
Silicon (Si) is 25.8% in Clarke number, and it is the second most frequent substance after oxygen on the earth. Silicon has a lot of its solid as silicon dioxide (SiO2), but most of it is “crystalline”. On the other hand, silica that is absorbed by humans and animals and plants is “amorphous” silica, which is contained in diatomaceous earth, plants and the like. In addition, amorphous silica not containing crystalline silica is generally rare and expensive as crystalline silica has been pointed out as carcinogenic to human body.
Rice hulls and rice straw contain a large amount of amorphous silica. Many methods have been devised to obtain amorphous silica by burning rice husks and rice straw. In the conventional process for producing amorphous silica from rice hulls, in the case of obtaining rum hull combustion products, the rice husks are first fired in a fluidized bed burning furnace and then in an externally heated rotary oven a second firing There was a general way to create combustion products of shells.